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Across 4. a plane closed figure with ten sides and ten angles. 5. plural of radius. 7. a parallelogram with four equal sides. 8. in a circle, an angle formed by two chords. Its vertex is on the circle. The measure of an inscribed angle equals one-half the measure of its arc. 9. a four-sided plane closed figure having equal sides and four right angles. Its opposite sides are parallel. 14. an angle formed outside the polygon by extending one side. In a triangle, the measure of an exterior angle equals the sum of the measures of the two remote interior angles. 15. many-sided plane closed figure. Triangle, quadrilateral, pentagon, and so on. 16. the total surface of all sides of a solid, or the total area of faces. 17. a polygon which contains at least one diagonal outside the figure. 20. a four-sided plane closed figure. The sum of its four angles equals 360°. 23. a plane closed figure with six sides and six angles. 26. the distance around a circle 27. the set of points on a circle that lie in the interior of a central angle. 28. a line, line segment, or ray that touches a circle at one point (cannot go within the circle). 29. a line segment connecting one vertex to another vertex, and not a side of the polygon.

Down 1. a plane closed figure with seven sides and seven angles. 2. circles with the same center. 3. the set of points all equidistant from a given point. 6. a polygon in which all diagonals lie within the figure. 7. a line segment whose endpoints lie one at the center of a circle and one on the circle. Also, the length of this segment. 10. a plane closed figure with eight sides and eight angles 11. an angle whose vertex is the center of the circle. The measure of a central angle is equal to the measure of its arc. 12. a four-sided plane closed figure having opposite sides equal and parallel and four right angles. 13. a polygon in which sides and angles are all equal. For example, a regular pentagon has five equal angles and five equal sides. 18. a plane closed figure with nine sides and nine angles 19. a line segment that contains the center and has its endpoints on the circle. Also, the length of this segment. (A chord through the center of the circle.) 21. a four-sided plane closed figure with only one pair of parallel sides, called bases. 22. a five-sided plane closed figure. The sum of its five angles is 540°. 24. a three-dimensional shape bounded by congruent parallel faces and a set of parallelograms formed by joining the corresponding vertices of the bases. 25. a six-sided solid. All sides are equal squares and all edges are equal. 26. a line segment joining any two points on a circle.